I've got a Brand-X bike bag that I've used twice to go over to Spain with (and it'll be used again in July).
I go a bit over the top i think, with the packaging, but would rather too much than not enough.
I take the rear mech off, discs off the wheels, handlebar off & tape to frame, wrap the whole thing in a combo of bubble wrap, pipe lagging etc. Pedals also come off, and I tape one crank arm to a chainstay to keep the cranks level. I've bodged a large block of foam that sits under the BB and shrouds the bottom of the chainrings to stop the outer getting mangled.
I've got a bike box from Halfords that I've cut down to fit into the bag as a fairly rigid liner.
One of my mates has got the same bag and another has got the CRC bag, which is also the same, but branded differently & none of us have had any bike damage over several trips.